Local order effects on the dynamical properties of critical fluids are taken into account by introducing a new slowly varying tensorial quantity which is related to the angular momentum of a group of correlated molecules. The theory is applied to an analysis of ultrasonic and light scattering...

The dynamical longitudinal correlation function of the low-temperature Heisenberg ferromagnet is studied in the collisionless regime. Taking into account the kinematical effects, a kinetic equation is derived in this regime describing the system only in terms of interacting spin-waves. The...

A variational principle is derived for the equilibrium Wigner distribution function of quantum statistical mechanics. This provides an alternative to the usual Wigner-Kirkwood expansion method of calculating quantum corrections to the structural and thermodynamic properties of systems. As an...

We show that the addition of external fields to the Dicke Hamiltonian removes the critical behaviour of the model. We analyse this result in terms of order parameter and conjugated field and compare with recent papers.

The static dielectric constant of nonpolar liquids is described by analyzing the pair distribution function and the dipole-dipole interaction into a finite set of Fourier components. In a mean field approximation the theory leads to a final formula that does not contain any adjustable parameter,...

The lower-bound variational approximation to the renormalization group transformation (LBV ARG) developed by Kadanoff is applied to the triangular Ising lattice. The approximation is applied to cells of different kinds and good agreement with the exacr results is obtained for a diamond-shaped...

The transition point of the five-state discrete vector model (planar Potts model) in two spatial dimensions is determined exactly by using a duality transformation. Also a comment is made on the justification of the uniqueness assumption of the transition point by the real space renormalization...

A general expression is derived for the effective shear viscosity of a simple regular array of suspended spheres for arbitrary values of the filling fraction. The resulting direction dependent viscosities are evaluated explicitly for the s.c., f.c.c. and b.c.c. lattices. We find that these...

The aim of this research is to study acceleration of test particles in random space-time dependent force fields, by using or generalizing some tools developed in particular for the study of stochastic differential equations with time-dependent random parameters. Preliminary results given here...

The Green's function and energy eigenvalues of an electron under the influence of a uniform electric field in a box with infinitely high sides is investigated. The second order correction to the energy eigenvalues is calculated by finding zeros of the wronskian and comparing with the value...